1. Field of the Invention
The invention relates to a capacitor element and a method of manufacturing the capacitor element in which a product of electrostatic capacity and voltage proof (CV product) per unit volume is higher as compared with electrolytic capacitors in related arts.
2. Background Art
An electrolytic capacitor using Al2O3 which is a kind of oxide of valve metal as a dielectric film is widely used from the past. The electrolytic capacitor is formed by combination of a dielectric film and an electrolyte component, being polarized. The area is intended to be expanded by roughening a surface of the Al2O3 film or some other ways, however, the attempt for higher capacity is reaching the limit. There is also a problem that applications are limited because the capacitor is polarized.
In order to solve the above problems and to allow the capacitor to have higher capacity, the following proposal is made. Specifically, in Patent Document 1, a method of obtaining a capacitor structure body is proposed, in which a porous substrate 4 having many pores 5 shown as a plan view in FIG. 35 is used as a mask, a first electrode 6a is formed by regularly arranging many pillar-shaped bodies 2a on a surface of a sheet electrode 2 on a capacitor substrate 1 by a thin-film deposition process or etching as shown in FIG. 36 as a cross-sectional view, next, a dielectric thin film 8 is formed by depositing a dielectric material having a permittivity of 100 or more on a surface of the first electrode 6a by using a MOCVD (organometallic vapor phase growing method), and further, a second electrode 6b is formed on a surface of the dielectric thin film 8 as shown in FIG. 37 as a cross-sectional view.
[Patent Document 1] JP-A-2003-249417
However, in the manufacturing method of the capacitor structure body as described in the above background art, the pillar-shaped bodies 2a are formed by using the porous substrate 4 as a mask, therefore, adhesion of the electrode material in the porous substrate 4 and inner walls of pores 5 of the porous substrate 4 and expansion of the pores 5 by the etching of the porous substrate 4 itself are liable to occur. Accordingly, there is a problem that it is difficult to obtain the pillar-shaped bodies 2a having an uniform cross-sectional shape and a desired linear dimension.
In addition, the dielectric thin film 8 is formed by depositing the dielectric material having the permittivity of 100 or more on the surface of the first electrode 6a on which the pillar-shaped bodies 2a stand by using the MOCVD, therefore, when the height of the pillar-shaped bodies 2a becomes high, the difference of film thickness in the dielectric thin film 8 is liable to occur at a region facing a source gas and directly coming into contact with the source gas and at a region not directly coming into contact with the source gas on the surface of the first electrode 6a. Therefore, there is a problem that it is difficult to stably obtain a capacitor in which a product of electrostatic capacity and voltage proof (CV product) per unit volume is high.